Despite great interest in the role of social networks as channels of political mobilization, few studies have examined which types of social networks work more effectively in recruiting political activists. Using the Citizen Participation Study data, this study shows that contrary to the conventional wisdom in the literature, there is little evidence that strong ties are more effective than weak ties in recruiting activists. Ties formed in civic associations, however, are more effective than other ties in recruiting protest participants. Neighborhood ties are more effective in recruiting community activists, but not in other types of activity. I conclude that the contents of relationships and the identities shared by two people, rather than tie strength, form the basis of interpersonal influence in political activism. (Contains 3 tables, 2 figures and 11 notes.)